Copyright © 2005 CloudyNights Telescope Reviews
William Optics ZenithStar 80
Tom Trusock – 5/05
Would you believe that I’m looking at 80mm refractors again?
Me either.
After the ED80, the 4 way shootout and the WO ED Triplet, I thought I was sated – at
least a bit. Then Mike from Astronomics offered to ship me a William Optics ZenithStar
80. I didn’t even hesitate. How could I?
You’d think someone who owns a 4” apo, an 18” reflector and various other scopes in
between probably wouldn’t be too interested in an 80mm class achro, right? Wrong! In
my opinion, apo or achro, an 80mm refractor is one scope that should be in everyone’s
arsenal.
As a dedicated visual observer, it’s mainly refractors and reflectors that interest me. For
most types of observing, I find reflectors offer the most bang for the buck, but I’m unable
to resist a small refractor.
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Copyright © 2005 CloudyNights Telescope Reviews
Optical quality is very important in an astronomical instrument, but make no mistake - If
you are talking only in terms of what you can see with a given telescope – aperture wins.
And significant aperture wins significantly. Nearly any of the inexpensive 8” reflectors
on the market should outperform any 80 mm scope. An 8” reflector will go deeper (let
you see fainter objects) and show you more detail – if the proper strictures are observed.
So if bigger is better, why do refractors command such a following?
Let’s consider the advantages of an 80mm refractor:
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Portability – an 80mm scope is FAR more portable than most of the 8” refractors
on the market. They say the best scope is the one you use most often, and while
I’d never be without at least an 8” dob, I have to admit it would be very tough to
part with a small refractor as well.
•
Quick cool down times – doublets especially are great for those quick peeks.
Many’s the night I’ve gotten home from work late and didn’t want to take the
time for the newt to cool down. Refractors (especially the doublets with well
designed lens cells) are usually ready for deep sky immediately, and lunar and
planetary in short order.
•
Reduced need for collimation – no need to tweak collimation before the beginning
of every session – most refractors will never need to be collimated by the end
user, and should even put up with a moderate amount of abuse without many
issues.
While a small quality apo may stretch the budget, small achros are far more reasonably
priced, and make a great compliment to a larger reflector. Their small size and light
weight helps ensure that you take them with you when traveling. Little refractors provide
sharp, wide fields of view for those immense clusters and do well for ole luna and the
planets too. If you haven’t scanned the summer milky way with a wide field scope, you
don’t know what you are missing out on.
Personally, I happen to think that every amateur needs (at least) two telescopes – a large
light bucket, and a small refractor. Think of them as different kinds of fishing tackle.
You’ll catch different things with each, but both are great ways to pass the time.
In this article, I take a look at one of the more popular 80mm achros on the market today
– the William Optics ZenithStar 80.
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Copyright © 2005 CloudyNights Telescope Reviews
William Optics ZenithStar 80
Price $399
Focal Length: 480mm
Aperture: Sample 1 - 80 (advertised), 7274mm Effective (approximation), Sample 2
– 78-80mm Effective
Weight: 5.3 lbs
Focal Ratio: f6 (Sample 2), f6.5 (Sample 1)
Highest Typical Effective Power: 120x160x
Focuser: 2” Crayford w/ rotate able back
ZenithStar 80
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•
•
•
•
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HOTS
Lightweight
Top Notch
Mechanics
Crayford
Focuser
Anodized OTA
Compression
Ring Fittings
2” Focuser
•
•
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NOTS
Some Optical
Vingetting on
early models
Lens can’t be
collimated by
end user
No elegant way
to mount an
RDF
This is a jet black glossy anodized optical tube assembly that’s offset beautifully by it’s
golden trim and slide on lens cap. This little piece of art comes complete with it’s own
briefcase style carrying case, 1.25” to 2” compression ring adapter, and L mounting
bracket (with 2 ¼-20 holes) for mounting on standard camera tripods. The L bracket now
comes with cork on the bottom, and is removable if you want to use the scope with a set
of rings instead (not supplied).
The crayford focuser is very smooth, noticeably smoother most typical rack and pinion
type focusers. It is adjustable and lockable. In addition, the entire focuser back rotates –
a boon for the astrophotographer, but less so for the visual observer as one can always
rotate the star diagonal. The dew shield retracts,
reducing the overall length of the tube for storage and
travel. Compression ring fittings are found
throughout.
The ZenithStar 80 is a gorgeous little telescope, that
gives a very high impression of quality. The glossy
anodizing (and yes, it IS anodizing) means no paint –
and no paint means no paint chips. While it’s a
prettier finish than traditional paint or enamel, I’m not
completely convinced it’s tougher. It’s probably
close enough that makes no difference however. The
one obvious down side is that it is so smooth, it shows
fingerprints very easily. You’ll want to keep a small
polishing cloth on hand. Suffice it to say, I found the
mechanics and fit and finish top notch as good as
those found in telescopes many times the ZS80’s
meager price.
The overall light weight of the telescope and included L-bracket means it couples fairly
well with just about any lightweight mount and tripod – even mounting on a medium
weight photo / video tripod in a pinch – a bonus for travelers who wish to go as light as
possible.
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Copyright © 2005 CloudyNights Telescope Reviews
The optics consist of an achromatic cemented doublet
and there is no provision for adjustment or collimation
of the lens in the cell.
This means that if the scope is miscollimated, there’s a
good chance it will have to go back to the dealer or
factory. Fortunately, it’s been my experience that
refractors are fairly durable, and very slight
miscollimation isn’t often that big of a deal.
That being said, the first ZS80 I was sent was rather
severely out of collimation. (DOH!) I contacted
Astronomics and exchanged it for another unit. Star
Excellent coatings
tests on the second showed it to be much better – still
not quite perfect, but overall it was good enough that I judged that it to have a negligible
effect on performance.
You may have noted that I approximated the effective aperture of the first samples as
somewhere around 72-74mm. (Before I go any further, I’d like to note that this has been
fixed in current telescopes – but we’ll get to that later.) The reduced aperture was due to
the rather unique baffle system WO chose to employ. Traditional baffles – or knife
edged baffles – are typically simply
thin strips of metal inside the OTA
that do not impinge into the light
path, but are strategically placed to
block incidental light in order to
increase contrast. Another common
method of baffling is to use a special
type of flocking paper (resembling
blackened sand paper) instead of the
knife edged baffles. Although some
pundits prefer the traditional method,
it’s been my experience that this
sandpaper approach also works well.
With this scope, WO is using a
different system entirely. The baffle
is an internally ridged cone that
attaches to the lens cell itself –
serving the dual purpose of the lens
cell retaining ring and baffle. It’s
The ZenithStar 80’s baffle system also serves as a lens
this light baffle cone that impinged
retaining ring, and was the cause of the vingetting. On the
left, the “fixed” baffle (note the extension tube), on the right,
on the light cone and thus reduced
the older one that created the vingetting problem – both are
the effective aperture.
shown attached to the lens cell.
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Copyright © 2005 CloudyNights Telescope Reviews
After discovering this in my initial testing, I e-mailed William Yang of William Optics,
and am happy to say the problem’s been corrected. Mr Yang now reports the clear
aperture of the ZS80 in their runs is currently around 78mm, and my measurements
(~80mm) confirm this. The solution was simplicity itself – an addition of an extension
on the existing baffle means the baffle does not stop down as quickly and thus does not
intrude into the optical path. The fix is easy to install and available from William Optics
– contact them or your dealer for more information.
Optics
First off, let me start by saying this is an achromat, and thus shows false color – if it’s
intrusive / significant or not is partly a personal issue, and partly dependent on your target
selection. As with anything, personal tolerances and experience with other telescopes
will play a large hand.
The scope took magnification well and effectively topped out around120x + on the moon
and planets before the image began to breakdown (this was largely due to intrusive
amounts of false color). You certainly could
have pushed it higher, however, it’s my
opinion that you really don’t gain much. The
optics had the definite snap to focus that is
typical of a good telescope, and star tests
showed it to possess acceptable optics for a
unit in this price class. After some side by
side comparisons with the WO ED Triplet, it’s
was obvious where the benefit of an apo lay the moon and planets. For wide field viewing,
and casual lunar and planetary work, either
Apo or Achromat delivers fine images - and in
my opinion, that is what this little achromat is
really designed for.
Other Thoughts
One minor fault of the ZenithStar is the lack
of an elegant way to mount an RDF. It’s such
a beautiful telescope, I cringe at the thought of
mounting it on the OTA with sticky tape, but
there’s currently no other recourse – at least
that I’m aware of.
The ZS 80 features a standard rotatable focuser
I had opportunity to work with William Optics
over the course of this article, and frankly,
they impressed me. Both David and William Yang are driven young men who have set
out to make a mark for themselves – and I have little doubt they will.
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Copyright © 2005 CloudyNights Telescope Reviews
I found them to be very good when it came to technical support and communications, for
the most part both returned e-mails quite promptly, and as a customer there would have
little doubt that they would do their best to ensure my satisfaction. I had a very positive
experience overall.
Bottom line?
For the advanced amateur, the one drawback
may be its lens design – the fact that it’s a
cemented achromatic doublet means that if it’s
out of collimation – it’s out. Contact WO or
your dealer for replacement. And yet, I think
there are certain advantages to this approach as
well. As a cemented doublet, it’s impossible for
the lenses to go out of collimation with respect
to each other – no matter how much banging
around it takes. This is one less source of
potential problems, and I think that given its target market, it was an excellent choice.
For the beginner or traveler, this is a nearly perfect small achromat. The optics are more
than acceptable given its modest cost. And as for the rest; lightweight and portable, the
fit and finish are fantastic – equal to scopes costing several times its price. This makes an
excellent introductory refractor for someone wanting to dip their toe into that pool, and
comes close to being the ultimate travel telescope for the more advanced amateur looking
for an option that won’t break the bank.
Available from :
Astronomics (among others)
http://www.astronomics.com
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